test: stabilize V2 CI test suites - #52159

What broke

• The CLI subprocess integration test added in feat(cli): allow disabling the background service #52107 fails on Windows in the V2 test run. James requested removing that test instead of changing its newline assertion. This removes only that test; the background-service implementation and remaining service tests stay intact.
• The Linux TUI stats test times out after the new-session-ID tests (feat(cli): create the session when --session names one that does not exist #51405) leave a process-wide home prompt draft behind. Start the stats test with a clean home draft. The two-file repro changed from 1 failure to 3 passes.

Verification

• bun test test/server-connection.test.ts --timeout 30000 --only-failures (packages/cli): 2 passed.
• bun test test/new-session-id.test.tsx test/stats.view.test.tsx --timeout 30000 --only-failures (packages/tui): 3 passed, three consecutive runs; failed before the fix.
• TUI suite excluding plugin-source.test.ts: 1,372 passed, 2 skipped. That excluded test requires newer Node than this host’s Node 18; it is not the CI failure.
• CLI/TUI package bun typecheck and root bun run lint passed. A local combined CLI test run hit Bun aborts while spawning concurrent service processes on this busy host; the focused changed-file run passes. Root bun run check hit a host-local TypeScript-Go SIGSEGV during the full parallel typecheck. CI will run the full Windows and Linux checks.

Requested by: @rekram1-node (Aiden via Slack)